This invention relates to an optical disc device. More particularly, the invention relates to an optical disc device and a storage system that protect information by encrypting data.
CSS (Content Scramble System), CPRM (Content Protection for Recordable Media) and AACS (Advanced Access Content System) are known as technologies having an encryption function for protecting copyrights from illegal copies in optical disc devices
US2008/00222095A1 (JP-A-2007-336058) (patent document 1) discloses a technology for utilizing the AACS in write-once media not capable of overwriting files. This patent document reads as follows. “In AACS, a plurality of keys is encrypted by using a device key assigned to each device for legally recording and reproducing content and a random number generated at random, is registered to a key file with the random number and is recorded to a recording medium. To reproduce the content, the encryption key registered to this key file is decrypted by using the random number and the device key to be reproduced. The content is reproduced by using the key so decrypted and the content is reproduced.”
The document further describes as follows. “MKB is referred to as “Media Key Block” and a media key Km is encrypted and recorded. The MKB records information of illegal devices, too, and the illegal devices are not allowed to take out the media key Km.” “The MKB encrypts and saves information necessary for generating a protected area key (Kpa) and contains Revoke Information (cancel information or nullification information). In other words, a security hole exists in a certain device key set and when a licenser inhibits the use of the corresponding device key Kd, revoke information about the corresponding device key Kd is described. The device having the corresponding device key Kd is not able to solve the cipher owing to this revoke information.”